Process of treating vulcanized-rubber waste.



" cage, in the county of UNITED STATES PATENT OFFICE.

wrcmsu A. summits, oi osroiioo, ILLINOIS.

PROCESS OF TFlE ATlNG VULGANIZEDBRUBBEQ WASTE,

, Specification of Letters latent.

Patented June 12, 1906.

Application filed May 22, 1905. Renewed Harsh 3, 191 36- Bsrill Ho. 317M953- To a whom it may con-corn:

Be it known that I, WILLIAM AtKoummu, a citizen of the United States, residing at Chi- Cook and State of illia new and useful Process Vulcanized-Rubher Waste, of

nuts, have invented of Treating which the following is a specification.

My. invention relates to the process of recovering rubber from vulcsmizea'l-rubbor waste, r vhioh includes so oration oi the fibrous material from the rub 381 by boiling the material in a iinely-dilided condition in the presence of chemicals for the purpose of dissolving the fiber and that of removing the sulfur or sulfur compounds and washing the product to cleanse it of the chemicals, pertiel-es offiber, and other impurities.

My invention relates more particularly to that part of the process thus generally described -hich pertains to effecting devuloenication of the rubber in the material undergoingrthe rubber-recovering treatment.

0 reconvert rubber scrap into a. material approaching the original rubber or rubber compound, so-thst it may be used again in the manufacture of rubber goods, devuleanizotion is necessary. As the process is comrnonly practiced, however, devulcsnizstion is only an sppareut and not a true condition,

since the contained sulfur is either not removed st all or is only acted upon and removed to a slight extent. The present practice may be divided into two methods of oporation. in the so-cellcd acid system of recovering 01' reclaiming rubber the material fiber is placed in a steam devulcs.mzer, where it is subjected to steam heat and steam contact under pressure at a temperature exceeding 300 Fahrenheit. The steam does not dissolve any sulfur and cannot, therefore, remove it but the high heat acting on the scoutchouc compound in a moist state causes a. partial decomposition, and consequently or tial destruction, of the ceoutchouo by re us ing a, portion of it to s resinous condition, w ioh enables adhesion of the mass in subsequent sheeting, molding, and other manipulation thereof. The material, however, has only little elasticity and but little tensible strength.

by the fact that analysis shows an actually increased sulfur percenta ie when sulfuric acid was the. acid used in t is fiber removing hyci step of the process and from the further tion on be effected without any addition of slight though place the material requires the addition to it of some sulfur; but in either case the curing of goods made from it is eilected in about onethird the time required for curing goods made fromvirgin rubber compounds. The other method employed involves the f socalled alkaline treatment, wherein the stock is subjected to the action of an alkaline solution, also at etemperature exceeding 300 Fahrenheit, for 24 period of time vary- .ing from six totwenty-four hours. In this case only a slight removal of the free sulfur is effected, the combined sulfur not bein attacked. The degree of resinification an consequent taclriness in this product is less. Hence the material has somewhat eater elasticity and tensile strength; but t at the treatment has produced no actual clevlrlcanination is proven by the fact that this g ggduot also cures or revu canizcs in sheet to of a thickness of about one-four of an inch in from four to six minutes, w caress a. similar virgin compound requires thirty utes or more for curing it.

True devulcanization must reduce the removal of at least a. considers 1e gprcentage of, the combined as well as the so sulfur. Furthermore, if he resultant material shall hove a value and qualities 'ap roximately equal to a. similar com ound me, e from virgin ceoutchouh-"%mn t 6' true nature of the esoutchouc itsel must not undergo change, In other words, resiniiicstion must be abso lutely avpided, and this can only be accomplished by a solvent which will actually dis: solve the sulfur erature. Such a solvent in my application No. 248,66, filed March is that described gen salts when addedto a mineral acid form a solvent for both fiber'andsulfur, the final That the scrolled devulcmusa, tion isnot properly devulcenizstion is proven of elasticity from new csoutohouc.

fsot that subsequent curing or revuloamzm for Letters Patent Serisl 6, 1905, which is I based on my discovery that the simple halo pr duct being full e ual to the original compdilnd from whio oods treated were as employed with similar compounds midssulfur i the degree of resinifieation has beenfgo owing to short steam-heat exposure, when much resmificstion has taken 1 at a non-destructive tom.

and the treat sulfuric acid oi 611 Bennie, to which a somewhat larger amount of hj 'drocldoric acid added and be whole diluted v. ilh about eightvolumes of Water, gives excellent r sults when boot and shoe or rubber-tire scrap is muted. Whether the hydrochloric acid is suilicieul is readily determinable by examining the material under treatment from time to time. Sulfuric acid alone turns the stock black, and it rcnmins dense and strong and is not devulcunized. Hydrochloric acid alone bleachcs the stock; but it also remains dense and strong, and is not devulcanized, while its action in removing the fiber alone is so slow as to render it an uneommercial proceeding, fully twenty-four hours of constant boiling being required, resulting in the loss oi a large quantity of the acid, which is the reason for its non employment. When, however, hydrochloric acid is present in sufiicient quantity with sulfuric a'cid, the fiber is corroded in a few minutes and is disintegrated in about thirty minutes. If the stock has been passed through is, screen of three-eighthsdiich mesh, the stock under treatment becomes white or light yellow, and as the sulfur is dissolved the stock' swells and becomes porous and very tender, oll'cring but little resistance to Btl'fitCliiT yet sl'iowing a true unvulcanized uni con ition. The best test I have found or determining when the solvents have done their we rk pro Jerly is to introduce a little red loud stock. l i hen such. stock turns gray or to a pale-y llow color, which takes about two hours, devulcanization is practically complete, and the ph 'sical condition of the stock is such that compounded matter like lime end lead, if they have not been dissolved,

drop out or can readily be removed by passng the material While wet through squeezing rolls.

slimline solution, which, however, Wil turn it black again, so that if a product of a light- It is advisable that this acid treated stock be subsequently boile in an gray color is desired in its natural state the operation ends (after washing inan alkaline water) with the one acid-boiling treatment, which is a sim )it! boiling, operation at 212 Fahrenheit. ii the material is kept sullicientl) wet, this temperature can be raised considembly to hast n the already rapid op eration. with safety. in this acid treatment, asin my aforesaid salted acid treatment, the addition of oxidizing substances which set free chlorin gas would be detrimental and destructive of the hydrochloric acid, besides causing the operation to be very obnoxious and dangerous, owing to the poisonous nature of free chlorin gas. My mixture of acids without oxidizing agents does not give objectiomilde lune-s or vapors in boiling so long as a ri-asol'iablc degree of. water dilution is umintuined.

Whiit I claim as new, and desire to secure by Letters Patent, is

l. In the chemical treatment, for the pur- )ose set forth, of vulcanized rubber or rub )(I compounds, the process of devulcanizing the some, which consists in boiling the material in a finely-divided condition, in an aqueous compound acid solution, practically free from oxidizing ingredients, of sulfuric acid, as the base, and an acid of the halogen elements of chlorin, bromin or iodin.

2. The recess of treating vulcanized rubher or rublier compounds, for the purpose set forth, which consists in boiling the material, in a finely-divided condition, inan aqueous solution, practically free fronioxidizin in-, gradients, of sulfuric acid and hydroch oric acid, and washing and drying the product.

3. The recess of treating vulcanized rubher or rub er compounds, for the purpose set forth, which consists in boiling the material, in a. finely-divided condition, in an aqueous compound acid solution, practically free from oxidizing ingredients, of sulfuric acid, as the base, and an acid of the halo en elements of chlorin, bromin or iodin, b0 i the product in an alkaline solution, and was ing and drying said product.

WILLIAM A. KUNEMAN.

In presence of- ,L. HEISLAB, J. H. LANDES. 

